A conventional optical parallel receiver includes a plurality of photodetectors for converting plural light signals, which are supplied from parallel transmission lines thereto, into electric signals, respectively, a plurality of differential amplifiers for amplifying difference voltages between the electric signals from the photodetectors and predetermined reference voltage signals, and a plurality of feedback circuits for feeding the reference voltages based on outputs of the differential amplifiers back to reference inputs of the differential amplifiers, respectively.
In this conventional optical parallel receiver, light signals are received in parallel by photodetectors to generate electric signals which are then supplied to the differential amplifiers. In each of the differential amplifiers, an electric signal is amplified by being compared to a reference voltage signal which is generated in accordance with the high and low values of the electric signal, and the differentially amplified signal is converted to a logic level signal.
According to the conventional optical parallel receiver, however, there are disadvantages in that the optical parallel receiver is large in size, because each of a differential amplifiers has the feedback circuit, and in that the reference voltage signal generated by the feedback circuit is unstable, when a received light signal continues high or low for a time, because the reference voltage signal follows the high or low input signal.